The idled San Onofre Nuclear Generating Station, if restarted, will not be capable of detecting further damage to vulnerable steam generators tubes before another shut down and inspection, the plant operator told federal safety regulators Wednesday.

In its proposal to restart San Onofre's Unit 2 reactor at partial power, plant operator Southern California Edison has proposed upgrades to listening devices attached to the outside of the plant's replacement steam generators. Another diagnostic tool, a software program known as GE Smart Signal, would monitor variances in plant equipment.

Edison executives made clear Wednesday that the enhanced monitoring will not provide real-time insights into wear on generator tubes, though they can help diagnose issues after future reactor shut downs and inspections.

The acknowledgement took place at a meeting in Rockville, Md., between nuclear commission and Edison staff to review a long list of concerns about the restart plan. Edison's responses will play a major role in whether the nuclear commission allows a restart. A decision could be made as soon as late-April or May.

Edison has proposed restarting Unit 2 at 70 percent power to dampen destructive vibrations among large thickets of tubing in each generator. The tubes are a barrier against the release of radiation and a component of the reactor's central cooling system.

Nuclear commission officials said it was implied that Edison's monitoring systems might be capable of detecting wear from tubes rubbing against other tubes.

Edison officials said the systems would be use as "backward looking" tools for investigating tube wear discovered during later inspections. The monitors cannot detect continued tube-on-tube wear, a crucial concern in restarting the plant, they said.

The rapid degradation of new steam generators installed in 2010 and 2011 has been traced to botched computer models of steam flows in the design phase, along with some manufacturing issues. The Unit 3 reactor has been sidelined indefinitely with more significant damage.

Edison officials also discussed how they planned to address technical specifications that require the plant be safe to operate at full power. Edison Vice President Tom Palmisano said the company was confident a new assessment by a contractor would show the plant can be run at 100 percent power.

Nuclear commission officials said more time was needed to consider whether Edison had addressed the issue.

Wednesday's meeting capped week of intense scrutiny of Edison's handling of the plant outage. State utilities regulators held public hearings on its investigation into possible customer rebates, while Edison outlined implications for investors in filings with the Securities and Exchange Commission.

The company has spent more than $400 million on repairs and replacement power -- costs it hopes to pass on to utility customers with the authorization of the California Public Utilities Commission.